Absorption refrigeration system

ABSTRACT

An absorption refrigeration system employing a pair of staged air-cooled absorbers and a pair of staged adiabatic evaporators. Strong solution from the generator passes first to the lowpressure absorber from which it flows through the high-pressure absorber back to the generator. Refrigerant liquid is flashcooled in the high-temperature adiabatic evaporator stage from which it passes to the low-temperature adiabatic evaporator for further flash-cooling and from which it is passed through a refrigerant heat exchanger for cooling a refrigeration load and back to the high-temperature adiabatic evaporator. Liquid transfer apparatus is provided for pumping liquid in the system driven by a single hermetically sealed motor, the shaft of which mounts at one end a centrifugal pump for circulating liquid refrigerant and at its opposite end a scoop pump for circulating absorbent solution. The shaft is journaled in tapered refrigerant cooled and lubricated bearings which additionally function as seal means to minimize the possibility of intermixture of refrigerant and solution.

United States Patent [72] Inventor Louis 11. Leonard, Jr.

Dewitt, N.Y. [21] App]. No. 20,769 [22] Filed Mar. 18, 1970 [45] Patented Nov. 30, 1971 [73] Assignee Carrier Corporation Syracuse,

[54] ABSORPTION REFRIGERATION SYSTEM 4 Claims, 1 Drawing Fig.

[52] U.S. Cl 62/476, 415/88, 415/89, 417/350 [51] int. Cl F25b 15/06 [50] Field of Search 62/476;

[56] References Cited UNITED STATES PATENTS 3,296,824 1/1967 Rohrs et al. 62/476 X 3,195,466 7/1965 Young 308/70 X 3,114,322 12/1963 Leonard, .lr. 308/70X 2,124,914 7/1938 Fottinger... 415/89 2,184,992 12/1939 Coons 415/89 Primary ExaminerMeyer Perlin Assisli'zr'it Examiner- P. D. Ferguson Attorneys-Harry G. Martin, Jr. and J. Raymond Curtin ABSTRACT: An absorption refrigeration system employing a pair of staged air-cooled absorbers and a pair of staged adiabatic evaporators. Strongsolution from the generator passes first to the low-pressure absorber from which it flows through the high-pressure absorber back to the generator. Refrigerant liquid is flash-cooled in the high-temperature adiabatic evaporator stage from which it passes to the lowtemperature adiabatic evaporator for further flash-cooling and from which it is passed through a refrigerant heat exchanger for cooling a refrigeration load and back to the high-temperature adiabatic evaporator. Liquid transfer apparatus is provided for pumping liquid in the system driven by a single hermetically sealed motor, the shaft of which mounts at one end a centrifugal pump for circulating liquid refrigerant and at its opposite end a scoop pump for circulating absorbent solution. The shaft is journaled in tapered refrigerant cooled and lubricated bearings which additionally function as seal means to minimize the possibility of intermixture of refrigerant and solution.

PATENTEDNUV 30 l97| 3, 624, 704

LOUIS H LEONARD, JR.

ATTORNEY ABSORPTION REFRIGERATION SYSTEM BACKGROUND OF THE INVENTION This invention relates to absorption refrigeration systems and to fluid transfer apparatus therefor. It is known to employ centrifugal pumps driven by one or more motors to circulate liquid refrigerant and absorbent solution in a refrigeration system. It is further known in the art to utilize a scoop pump in the absorption solution circuit in place of a centrifugal pump, since scoop pumps have among their advantages simplicity of construction and generally will not cavitate even though a relatively small quantity of fluid is fed to them. Further, scoop pumps have other advantages, such as a low suction head requirement, the ability to pump mixtures of noncondensables and liquids and can be run with no liquid therein, if required, without deleterious results.

However, scoop pumps characteristically require substantial torque to place them in operation after a machine shutdown in order to remove any absorbent solution which drains into the scoop pump housing when machine operation stops. However, once the scoop pump is in operation, the torque necessary to keep the solution in circulation is much reduced. Accordingly, the use of a single large motor to drive both a scoop solution pump combined with a centrifugal refrigerant pump is especially desirable because of the economy of using one rather than two motors and because a given percentage overload on the larger motor results in more actual extra horsepower being available for starting the scoop pump than if separate motors are used. Further, the horsepower required by the refrigerant pump is several times that normally required by the scoop pump so that more excess torque and horsepower are available for the scoop pump by combining the pumps. Such an arrangement, however, requires an effective seal between the refrigerant and solution pumps for efficient operation.

SUMMARY OF THE INVENTION In accordance with this invention, there is provided an absorption refrigeration machine having a fluid transfer apparatus for pumping liquids in the system. Liquid refrigerant and absorbent solution are circulated in the absorption refrigeration system by a preferred embodiment of the fluid transfer apparatus which includes a single hermetically sealed motor supporting centrally thereof a drive shaft which mounts at one end a centrifugal pump and at its opposite end a scoop pump. The centrifugal pump is effective to circulate liquid refrigerant from the evaporator through a sensible-type heat exchanger and back to the evaporator. The scoop pump is of the multicompartment type and functions to pass solution to and from the absorber and generator. A hermetic motor drives a pump drive shaft which is journaled in two sets of tapered bearings, one bearing in each set being constructed of a graphitic material. The drive shaft is centrally passaged partially along the length thereof for passing chilled water from the pumphousing through one end of the motor casing and into heat transfer relationship with the bearings and with the rotor to cool and lubricate the same.

In accordance with this invention, a single motor is utilized to drive a plurality of pumps which may include both the refrigerant circulation pump and the solution circulation pump, thereby significantly reducing the initial cost and maintenance expense of the absorption refrigeration machine. The substantial torque required only upon startup of the scoop solution pump and the required additional horsepower is available by overloading the large motor which also drives the chilled water pump. Motor costs are reduced by this invention, and there is also eliminated a second set of auxiliary motor equipment, such as starters, interconnecting wiring, controls and other items. Further, a simple and effective arrangement is provided for motor cooling and bearing lubrication and cooling.

BRIEF DESCRIPTION OF THE DRAWING The single view is a schematic flow diagram, partially in cross section, of an absorption refrigeration machine embodying a preferred liquid transfer apparatus in accordance with this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In accordance with a preferred embodiment of this invention, there is provided an absorption refrigeration system which utilizes water as a refrigerant and an aqueous solution of lithium bromide as an absorbent. Strong solution" as referred to herein is a concentrated solution of lithium bromide, which is strong in absorbing power, and weak solution" is a dilute solution of lithium bromide which is weak in absorbing power. Intermediate solution" refers to solution intermediate in absorbing power and concentration between strong and weak solutions.

Referring to the drawing, there is shown an absorption refrigeration system comprising a generator 10, a refrigerant condenser 11, a high-temperature adiabatic evaporator 12, a low-temperature adiabatic evaporator 13, a high-pressure absorber 14, a low-pressure absorber 15, a sensible fan coil refrigerant heat exchanger 16, an absorbent solution heat exchanger 17, and liquid transfer apparatus 18 connected in a system to provide refrigeration. A purge unit 21 may be employed to remove relatively noncondensable vapors from the system.

Generator 10 comprises a boiler preferably having a shell 25, a plurality of internal flue tubes 26, a heat source such as gas burner 27, and a flue gas collector 28. Weak absorbent solution enters the generator and is boiled therein to concentrate the absorbent solution by vaporizing refrigerant. The concentrated or strong solution is discharged from the generator through strong solution passage 30.

The strong solution leaving the generator is preferably cooled by passing through the shell side passage of solution heat exchanger 17 from which it passes through fluid transfer apparatus 18 and passage 152 to low-pressure absorber l5.

Low-pressure absorber 15 preferably comprises a plurality of vertically disposed finned absorber tubes 36, opening at their upper ends into a low-pressure vapor header 35. Strong solution is discharged from strong solution passage 152 into vapor header 35 of low-pressure absorber 15. The lower ends of absorber tubes 36 open into a low-pressure liquid header 38. A fan 39 passes ambient cooling air over the exterior surfaces of the absorber tubes of both the highand low-pressure absorbers to cool absorbent solution passing down through the tubes. The upper ends of absorber tubes 36 project upwardly into vapor header 35 to form a weir for distributing the strong solution onto the interior walls of the absorber tubes. The strong solution passes downwardly through absorber tubes while being cooled by ambient air passing over the exterior surfaces of the tubes, thereby maintaining a low solution vapor pressure or saturation temperature. Refrigerant vapor from low-temperature evaporator 13 enters the ends of absorber tubes 36 from vapor header 35 and passes downwardly therein, concurrently with the strong solution. This refrigerant vapor contacts the strong absorbent solution within absorber tubes 36, and is absorbed therein, thereby forming absorbent solution of intermediate strength. The intermediate solution is collected in liquid header 38 from which it passes through a siphon tube 40 into conduit 44, leading to fluid transfer apparatus 18.

High-pressure absorber 14 is similarly provided with a plurality of vertically disposed finned absorber tubes 46 having their upper ends opening into a high-pressure vapor header 45 to establish a level of intermediate strength absorbent solution therein. The lower ends of the high-pressure absorber tubes 46 open into high-pressure liquid header 48. Intermediate strength absorbent solution from liquid header 45 together with refrigerant vapor from high-temperature evaporator 12 flows downwardly through absorber tubes 46 while the absorbent solution is cooled therein by passing ambient air over the exterior surfaces of the absorber tubes.

The absorption of refrigerant vapor into the intermediate solution passing downwardly through absorber tubes 46 dilutes the intermediate solution and the resulting weak solution is collected in liquid header 48. Weak solution passes out of liquid header 48 through siphon tube 50 into weak solution reservoir 61.

Weak solution from reservoir 61 drains through passage 154 into liquid transfer apparatus 18 from which it is pumped through weak solution passages 156 and 63 to generator for reconcentration.

The refrigerant vapor formed by boiling weak solution passes out of the generator through refrigerant vapor line 65 into vapor header 70 of refrigerant condenser 11. Refrigerant condenser 11 preferably comprises a plurality of vertically disposed finned condenser tubes 71 opening upwardly into vapor header 70 and downwardly into liquid header 72. Cooling air is passed over the exterior surfaces of finned tubes 71 by a suitable fan. The refrigerant vapor is condensed within condenser tubes 71 by heat exchange with the air and the condensed refrigerant passes through the refrigerant liquid line 74 and float valve 160 into high-temperature refrigerant evaporator 12.

High-temperature adiabatic evaporator 12 may comprise a shell 80 from which a refrigerant vapor passage 84 extends to vapor header 45 of the high-pressure absorber. The warm refrigerant, upon entering high-temperature evaporator 12, is adiabatically flash-cooled to the corresponding absorber pressure and saturation temperature. The unevaporated major portion of liquid refrigerant in adiabatic evaporator 12 is cooled due to the heat of evaporation which is absorbed from the liquid in vaporizing the small flashed portion of the refrigerant. The cooled refrigerant liquid reaching the bottom of the high-temperature adiabatic evaporator is discharged by gravity flow through refrigerant passage 85, having a liquid trap 86, into low-temperature adiabatic refrigerant evaporator 13. Low-temperature evaporator 13 is physically disposed at a vertically lower elevation than high-temperature evaporator 12 to enable gravity flow of liquid refrigerant from the hightemperature evaporator to the low-temperature evaporator through trap 86 which provides a liquid seal to maintain the pressure difference between the evaporator stages.

The cooled refrigerant discharged from the high-temperature adiabatic evaporator 12 into the low-temperature adiabatic evaporator 13 is again adiabatically flash-cooled to a still lower temperature. The cold refrigerant liquid reaching the bottom of low-temperature adiabatic evaporator 13 is discharged by gravity flow through cold refrigerant liquid passage 95 into a suitable cold refrigerant reservoir 96. The cold refrigerant passes through passage 161 to fluid transfer apparatus 18 by which it is pumped through heat exchanger 16 and returned through passage 105 to high-temperature evaporator 12.

Fluid transfer apparatus 18 of this invention comprises a single hermetically sealed motor 19 having a generally cylindrical outer casing 110 to which is attached by fastening means 111 an annular flange member 112 providing support through bolt means 113 for a bearing support member 114 shaped to include an annular collar portion 115 integral with radially inwardly and radially outwardly directed portions 116 and 117, respectively. A cover member 120 having flange 119 is attached to flange 112 by bolts 118 and forms a centrifugal pump chamber 122. Impeller 123 of the centrifugal pump is supported at one end upon drive shaft 124 which is secured to motor rotor 125 positioned in magnetically inductive relation through a nonferromagnetic housing 127 with motor stator 128 attached to the inner diameter of motor housing 1 l0. Stator 128 has windings 128a connected to a source of electrical energy.

Bearing support member 114, including portion 115 thereof, maintains bearing means 129 comprising spring 136, an annular, spring biased, conical bearing member 130 and a mating conical bearing member 131 in running relation with drive shaft 124 journaled in the bearing means 129. Bearing member 131 functions as a thrust and sleeve bearing and is desirably constructed of a graphitic material, while the bearing member may be stainless steel or the materials of the bearing members may be reversed. Bearing member 130 is axially movable in annular member 115 and biased into sealing engagement with bearing member 131 by spring 136 to compensate for bearing wear, and bearing member 129 is relative- Iy immovable in an axial direction with respect to drive shaft 124. A similar conical bearing 133 is also provided adjacent the opposite end of theshaft and, as shown, is secured in bearing support member 137. Bearing 133 comprises a conical bearing member 134 secured on shaft 124 mating with a conical bearing member 135 which is fixed on member 138 by fastening means 132 in annular sleeve member 137 to which is welded or otherwise secured an annular end member 138 connected to a radially inwardly directed flange portion 139 on the motor housing 110. A labyrinth seal 163 is provided between the discharge of impeller 123 and interior chamber 173.

Motor housing 110 is provided at the end adjacent the bearing 133 with an integral collar portion 140 coaxially spaced from drive shaft 124. Shaft 124 supports a rotatable scoop pump pan assembly 141 which is positioned within a stationary hermetic pump housing 142. The pan assembly 141 comprises three connected channel-shaped pans 143, 144 and 145, defining therewithin three solution circulation chambers for transferring through suitable conduit means intermediate, strong and weak solution, respectively. Discharge nozzle 146 forming a part of conduit 44 extends into pan 143 for draining into this chamber intermediate strength solution from header 38 of low-pressure absorber 15. The intermediate solution is impelled into eduction orifice 147 of conduit 148 and transferred thereby to header 45 of high-pressure absorber 14.

Solution circulation chamber 144 has disposed therein discharge nozzle 149 forming a part of conduit 150 for passing strong solution thereto from generator 10. The strong solution is pumped from chamber 144 by means of eduction orifice 151 of conduit 152 and transferred thereby to header 35 of low-pressure absorber 15.

Weak solution from liquid header 48 of high-pressure absorber l4 drains into chamber 145 through discharge nozzle 153 of conduit 154 and is pumped from this chamber through eduction orifice 155 of conduit 156 for transfer through solution heat exchanger 17 and conduit 63 to generator 10. The solution is concentrated in generator 10 and the resulting water vapor is passed to condenser 11. A float valve 160 is located in line 74 to maintain a pressure difference and to prevent noncondensables from passing to high-temperature evaporator 12.

Means is provided to cool the rotor 125 and to also lubricate and cool the bearing means 129 and 133. Cold liquid refrigerant drains from reservoir 96 communicating with lowtemperature evaporator 13 through conduit 161 into the interior of pump impeller 123. A portion of the liquid enters the motor chamber through passage 162 in bearing support member 114. This refrigerant flows first radially inwardly along passage 164 between bearing support portion 117 and flange member 112 and then along axial passage 165 defined in part by annular flange 115 and the inner surface of the annular casing 127. The cold refrigerant thereby cools the bearings 129 and 133 and as it moves axially through the motor chamber, rotor 125 within casing 126 is also cooled. Shaft 124 is axially passaged as at along a portion of the length thereof and provided at opposite ends of the passage is a pair of openings 171 and 172. Cold liquid refrigerant which has cooled and lubricated bearing means 129, rotor 125 and bearing 133 passes into shaft opening 171, flows through shaft passage 170 and is discharged through shaft opening 172 into space 173. The refrigerant then flows through aperture in impeller 123 to be directed therefrom through conduit 180 to sensible-type heat exchanger 16.

In addition to being cooled and lubricated by liquid refrigerant, bearing means 133 is lubricated by solution. This is accomplished by provision of pickup scoop 175 having an eduction orifice 176 positioned adjacent the bottom of scoop pump housing 142 and a discharge nozzle 177 leading into the tubular end portion 140 on motor housing 110. In this manner, solution which drains into the bottom of the pump housing upon machine shutdown, or which spills or splashes over from the scoop pump pans during pan rotation, is pumped by the pickup scoop 176 and discharged against the end face of bearing means 133 to provide cooling. Of course, by constructing the components of the bearing means 129 and 133 as shown in the drawing, there is essentially no likelihood of intermixing of refrigerant and solution.

lt can be seem from the foregoing that by provision of a single hermetically sealed motor which mounts on a single common shaft a centrifugal refrigerant circulation pump and a scoop-type solution circulation pump, the initial cost and maintenance expenses of the absorption refrigeration machine are markedly reduced. The bearing means disclosed not only function effectively as bearings, but also seal the liquid refrigerant from the absorbent solution. Additionally, novel means are provided to assure that the motor does not become overheated and that the bearings are at all times adequately lubricated and cooled.

The capacity and power required to operate the refrigerant pump may be on the order of about times the power required by the solution pump. Consequently, the excess torque available from the relatively large motor required to operate the refrigerant pump is available to operate the scoop pump before the pump housing cleared of solution. Also, by overloading the motor during the time the scoop pump is removing liquid from the bottom of housing 142, a much larger amount of excess horsepower is available at the time it is needed to run the scoop pump, than if a separate refrigerant pump motor were used.

Various changes and modifications may of course be effected in the machine herein disclosed without departing from the spirit of the invention or the scope of the subjoined claims.

I claim:

1. An absorption refrigeration system comprising a generator for boiling absorbent solution to concentrate the solution by vaporizing refrigerant therefrom; a condenser for condensing refrigerant vapor formed in the generator; an evaporator for evaporating refrigerant condensed in the condenser to produce refrigeration; an absorber for absorbing refrigerant vapor formed in the evaporator into absorbent solution concentrated in the generator; and fluid transfer apparatus for pumping liquid in the system, said fluid transfer apparatus comprising a sealed housing, a centrifugal refrigerant pump disposed within said housing and connected in said system for pumping refrigerant therein, a scoop solution pump disposed within said housing and connected in said system for pumping absorbent solution therein, said refrigerant pump having a relatively large capacity compared with said solution pump, said scoop pump including a scoop pump pan member, an inlet conduit for discharging absorbent solution into said scoop pump pan member, a stationary eduction conduit disposed in said housing and having an eduction orifice in said pan member for receiving absorbent solution impelled therein by rotation of said pan member, drive means secured to said pan member for rotating the pan within said housing, and a combined bearing and sealing means disposed within said housing between said centrifugal refrigerant pump and said scoop solution pump for sealing the centrifugal pump from said scoop pump to prevent substantial leakage and mixing of refrigerant and absorbent solution between said pumps, said combined bearing and sealing means including a pair of tapered bearing members having mating conical bearing and sealing surfaces, one of said bearing members being mounted on and sealingly engaged with a rotating portion within said housing and the other of said bearing members being mounted on and sealingly engaged with a stationary portion in said to prevent intermixmg of absorbent solution and housing refrigerant, said bearing and sealing arrangement including resilient means urging said conical bearing and sealing surfaces into engagement with each other.

2. An absorption refrigeration system as defined in claim 1 wherein said drive means comprises a motor rotor mounted for rotation in said housing and supported therein by said bearing and sealing means, and a motor stator mounted exteriorly of said housing in inductive relation with the rotor member in said housing.

3. An absorption refrigeration system as defined in claim 1 including passage means for passing refrigerant from the refrigerant pump to said combined bearing and sealing means to cool the bearing and sealing means during operation of the system, and passage means for returning the refrigerant from said combined bearing and sealing means to said refrigerant pump.

4. An absorption refrigeration system as defined in claim 1 including an eduction conduit having an eduction orifice disposed in said housing between a wall thereof and said scoop pump pan member for receiving and removing liquid from between the pan member and the housing, said eduction conduit having a discharge orifice positioned for passing liquid to said combined bearing and sealing means for cooling and lubricating said bearing and sealing means.

i t t 

1. An absorption refrigeration system comprising a generator for boiling absorbent solution to concentrate the solution by vaporizing refrigerant therefrom; a condenser for condensing refrigerant vapor formed in the generator; an evaporator for evaporating refrigerant condensed in the condenser to produce refrigeration; an absorber for absorbing refrigerant vapor formed in the evaporator into absorbent solution concentrated in the generator; and fluid transfer apparatus for pumping liquid in the system, said fluid transfer apparatus comprising a sealed housing, a centrifugal refrigerant pump disposed within said housing and connected in said system for pumping refrigerant therein, a scoop solution pump disposed within said housing and connected in said system for pumping absorbent solution therein, said refrigerant pump having a relatively large capacity compared with said solution pump, said scoop pump including a scoop pump pan member, an inlet conduit for discharging absorbent solution into said scoop pump pan member, a stationary eduction conduit disposed in said housing and having an eduction orifice in said pan member for receiving absorbent solution impelled therein by rotation of said pan member, drive means secured to said pan member for rotating the pan within said housing, and a combined bearing and sealing means disposed within said housing between said centrifugal refrigerant pump and said scoop solution pump for sealing the centrifugal pump from said scoop pump to prevent substantial leakage and mixing of refrigerant and absorbent solution between said pumps, said combined bearing and sealing means including a pair of tapered bearing members having mating conical bearing and sealing surfaces, one of said bearing members being mounted on and sealingly engaged with a rotating portion within said housing and the other of said bearing members being mounted on and sealingly engaged with a stationary portion in said housing to prevent intermixing of absorbent solution and refrigerant, said bearing and sealing arrangement including resilient means urging said conical bearing and sealing surfaces into engagement with each other.
 2. An absorption refrigeration system as defined in claim 1 wherein said drive means comprises a motor rotor mounted for rotation in said housing and supported therein by said bearing and sealing means, and a motor stator mounted exteriorly of said housing in inductive relation with the rotor member in said housing.
 3. An absorption refrigeration system as defined in claim 1 including passage means for passing refrigerant from the refrigerant pump to said combined bearing and sealing means to cool the bearing and sealing means during operation of the system, and passage means for returning the refrigerant from said combined bearing and sealing means to said refrigerant pump.
 4. An absorption refrigeration system as defined in claim 1 including an eduction conduit having an eduction orifice disposed in said housing between a wall thereof and said scoop pump pan member for receiving and removing liquid from between the pan member and the housing, said eduction conduit having a discharge orifice positioned for passing liquid to said combined bearing and sealing means for cooling and lubricating said bearing and sealing means. 